This document specifies the TinyIPFIX protocol that is used for transmitting smart-metering data in constrained networks such as IPv6 over Low-Power Wireless Personal Area Networks (6LoWPAN, RFC 4944). TinyIPFIX is derived from IP Flow Information Export (RFC 7011) and adopted to the needs of constrained networks. This document specifies how the TinyIPFIX Data and Template Records are transmitted in constrained networks such as 6LoWPAN and how TinyIPFIX data can be converted into data that is not TinyIPFIX in a proxy device.